114 HOW CROPS GROW. 
ing organism existed in union with organic acids; the lat 
te1 being destroyed by burning. 
It also occurs in combination with lime in the tissues of 
many plants. Its compounds with bases are carbonates 
to be noticed presently. When a carbonate, as marble or 
limestone, is drenched with a strong acid, like vinegar or 
muriatic acid, the carbonic acid is set free with effer- 
vescence 
Cyanogen, Sym. CN.—This important compound of Carbon and 
Nitrogen is a gas which has an odor resembling that of peach-pits, 
and which burns on contact with a lighted taper with a fine purple flame. 
In its union with oxygen by combustion, carbonic acid is formed, and 
nitrogen set free, 
CN+20=CO,. +N. 
Cyanogen may be prepared by heating an intimate mixture of two parts 
by weight of ferrocyanide of potassium, (yellow prussiate of potash,) and 
three parts of corrosive sublimate. The operation may be conducted in 
a test tube or small flask, to the mouth of which is fitted a cork pene- 
trated by a narrow glass tube. On applying heat, the gas issues, and 
may be set on fire to observe its beautiful flame. 
Cyanogen, combined with iron, forms the Prussian blue of commerce, 
and its name, signifying the blue-producer, was given to it from that cir- 
cumstance. 
Cyanogen unites with the metallic elements, giving rise to a series of 
bodies which are termed Oyanides. Some of these often occur in small 
quantity in the ashes of plants, being produced in the act of burning by 
the union of nitrogen with carbon anda metal. For this result, the 
tem: perature must be very high, carbon must be in excess, the metal 
is usually potassium or calcium, the nitrogen may be either free nitrogen 
of the atmosphere or that originally existing. in the organie matter. 
With hydrogen, cyanogen forms the deadly poison hydrocyanie or prus- 
sic acid, H Cy, which is produced from amygdaline, one of the ingre- 
dients of bitter almonds, peach, and cherry seeds, when these are crush- 
ed in contact with water. 
When a cyanide is brought in contact with steam at high temperatures, 
‘t is decomposed, all its nitrogen being converted into ammonia. 
Cyanogen is a normal ingredient of one common plant. The ou of 
mustard is the sulpho-cyanide of allyle, Cs Hs CNS. 
SULPHUR AND ITS COMPOUNDS. 
Sulphur, Sym. S, at. wt. 32.—The properties of this 
element have been already described, (p. 42.) Some of 
